Ammonia gas injection flow control method and device

Abstract

The invention discloses an ammonia gas injection flow control method, which comprises the following steps that: after an engine is detected to be started, a controller sends a self-learning instruction to the engine, and the self-learning instruction is used for instructing to learn the amount of injected ammonia gas when the operation working condition of the engine reaches a preset working condition; and after it is determined that the ammonia gas in the SCR device is emptied and the operation disclosure of the engine reaches the preset working condition, the injection electromagnetic valve is controlled to inject the ammonia gas according to the duty ratio under the preset working condition. And the tail gas conversion efficiency of the engine is obtained, whether the tail gas conversion efficiency meets preset conditions or not is judged, if yes, it is indicated that the treated tail gas contains nitric oxide, injection of ammonia gas is insufficient, and the flow curve of the injected ammonia gas is corrected. Namely, after it is detected that the treated tail gas contains nitric oxide, self-learning is conducted on the ammonia gas injection amount, so that the corrected flow curve can offset the problem that the injection amount is insufficient due to aging of the injection electromagnetic valve, and the tail gas conversion efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of exhaust gas treatment technology, specifically to a method and apparatus for controlling the flow rate of ammonia injection. Background Technology

[0002] Currently, the main technological approach used to address NOx emissions is Selective Catalytic Reduction (SCR), which uses ammonia (NH3) to reduce NOx into harmless N2. Urea or ammonia can be chosen as the reducing agent for SCR.

[0003] In this method, urea is chosen as the reducing agent, and it is evaporated and hydrolyzed to produce ammonia gas through heating. Urea is a liquid at room temperature, making it convenient to calculate the amount of reducing agent by measuring the volume of the injected liquid during injection metering. However, using urea requires a high exhaust temperature and is prone to recrystallization, posing significant challenges for subsequent use and maintenance. In the solid ammonia gas supply system, ammonia gas is desorbed by heating the ammonia storage tank, and then injected via a solenoid valve after passing through a pressure reducing valve.

[0004] However, during the actual injection process of the solenoid valve, there may be problems such as aging of the solenoid valve spring and dirt on the nozzle, which will cause changes in the actual injection volume of ammonia, affecting the SCR after-treatment effect and causing NOx emissions to exceed the standard. Summary of the Invention

[0005] In view of this, embodiments of this application provide an ammonia injection flow control method and apparatus, which, by correcting the ammonia injection quantity, meets the actual requirements of SCR and avoids NOx emissions exceeding the standard.

[0006] To address the above problems, the technical solutions provided in this application are as follows:

[0007] In a first aspect of this application, an ammonia injection flow control method is provided, the method being applied to a controller, comprising:

[0008] In response to engine start-up, a self-learning command is sent to the engine. The self-learning command is used to instruct the flow curve to be self-learned when the engine's operating conditions reach preset conditions. The flow curve is used to indicate the duty cycle of the injection solenoid valve when injecting ammonia under different operating conditions of the engine.

[0009] If it is determined that the ammonia in the selective catalytic reduction (SCR) unit is emptied and the engine's operating conditions reach the preset conditions, the injection solenoid valve is controlled to inject ammonia according to the duty cycle under the preset conditions.

[0010] Obtain exhaust gas conversion efficiency;

[0011] If the exhaust gas conversion efficiency meets the preset conditions, the flow rate curve is corrected based on the exhaust gas conversion efficiency.

[0012] In a second aspect of this application, a controller is provided, the controller comprising:

[0013] The sending unit, in response to engine start-up, sends a self-learning command to the engine. The self-learning command is used to instruct the flow curve to perform self-learning when the engine's operating condition reaches a preset operating condition. The flow curve is used to indicate the duty cycle of the injection solenoid valve when injecting ammonia under different operating conditions.

[0014] The control unit is used to control the injection solenoid valve to inject ammonia according to the duty cycle under the preset operating conditions if it is determined that the ammonia in the selective catalytic reduction (SCR) unit is emptied and the engine operating conditions have reached the preset operating conditions.

[0015] The acquisition unit is used to acquire the exhaust gas conversion efficiency;

[0016] The correction unit is used to correct the flow curve according to the exhaust gas conversion efficiency if the exhaust gas conversion efficiency meets the preset conditions.

[0017] In a third aspect of this application, a controller is provided, comprising: a memory and a processor;

[0018] The memory is used to store computer-readable instructions or computer programs;

[0019] The processor is configured to read the computer-readable instructions or the computer program to cause the electronic device to perform the method described in the first aspect.

[0020] In a fourth aspect of this application, a vehicle is provided, the vehicle comprising: the controller described in the second or third aspect and an engine;

[0021] The controller is used to control the injection solenoid valve in the engine to inject ammonia gas according to a preset duty cycle;

[0022] The engine is used to provide power to the vehicle.

[0023] In a fifth aspect of this application, a computer-readable storage medium is provided, wherein instructions are stored therein, which, when executed on a device, cause the device to perform the method described in the first aspect.

[0024] In a sixth aspect of this application, a computer program product is provided that, when the computer program product is run on a computer, causes the computer to perform the method described in the first aspect.

[0025] Therefore, the embodiments of this application have the following beneficial effects:

[0026] In this application, after detecting engine start, the controller sends a self-learning command to the engine. This command instructs the controller to learn the amount of ammonia injected when the engine's operating conditions reach a preset level. After confirming that the ammonia in the SCR unit is emptied and the engine's operating conditions have reached the preset level, the controller controls the injection solenoid valve to inject ammonia according to the duty cycle under the preset condition. The engine's exhaust gas conversion efficiency is obtained, and it is determined whether the efficiency meets a preset condition. If it does, it indicates that the treated exhaust gas contains nitrogen oxides, and the ammonia injection is insufficient. Therefore, the flow rate curve is corrected. The flow rate curve indicates the duty cycle corresponding to the injection solenoid valve's ammonia injection under different engine operating conditions. In other words, after detecting that the treated exhaust gas contains nitrogen oxides, this application indicates that the ammonia injection solenoid valve may be aging, causing a change in the actual ammonia injection amount. Therefore, the controller performs self-learning on the ammonia injection amount so that the corrected flow rate curve can compensate for the insufficient injection amount caused by the aging injection solenoid valve, thereby improving the exhaust gas conversion efficiency. Attached Figure Description

[0027] Figure 1 A flowchart of an ammonia injection flow control method provided in this application embodiment;

[0028] Figure 2 A flow curve correction framework diagram provided for embodiments of this application;

[0029] Figure 3 A controller structure diagram provided in an embodiment of this application;

[0030] Figure 4 Another controller structure diagram provided in this application embodiment;

[0031] Figure 5 This is a vehicle structure diagram provided for an embodiment of this application. Detailed Implementation

[0032] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0033] Currently, solid ammonia systems, which typically use strontium chloride as an adsorbent to directly adsorb ammonia, are becoming a new option for SCR systems in passenger vehicles. In solid ammonia supply systems, ammonia is desorbed by heating the ammonia storage tank, and then injected via a solenoid valve after passing through a pressure reducing valve. During the actual injection process, issues such as solenoid valve spring aging and nozzle contamination may occur, leading to variations in the actual ammonia injection volume and affecting the SCR aftertreatment effect.

[0034] Based on this, this application provides an ammonia injection quantity control method, which performs precise metering and self-learning on the actual ammonia injection quantity in the solid ammonia system, so as to dynamically adjust the ammonia injection quantity through self-learning, avoid the actual injection quantity being too low due to solenoid valve spring aging or nozzle dirt, and improve the tail gas conversion efficiency.

[0035] The equivalence ratio, also known as the "fuel coefficient" or "excess fuel coefficient," is the ratio of the amount of air theoretically required for complete combustion to the actual amount of air supplied. A equivalence ratio greater than 1 indicates that the actual amount of air in the combustible mixture is less than the theoretically required amount, meaning insufficient air. Conversely, a equivalence ratio less than 1 indicates that the actual amount of air in the combustible mixture exceeds the theoretically required amount, meaning excess air. The equivalence ratio is essentially the reciprocal of the equivalence air coefficient.

[0036] A solenoid valve is a controllable switching device. Its passage opens or closes at different times depending on the position of a reciprocating conical valve core, thereby controlling the flow rate of liquids or gases. The duty cycle of a solenoid valve refers to the proportion of time the valve is energized within its cycle. For example, if the operating cycle is 10 seconds, with 5 seconds of energization and 5 seconds of de-energization, then the duty cycle of the solenoid valve is 50%.

[0037] The duty cycle of a solenoid valve directly affects its switching frequency and the heat generated by the electromagnet. A higher duty cycle results in a higher operating frequency and greater heat generation from the electromagnet. Therefore, the duty cycle must be set according to specific conditions to prevent premature damage to the solenoid valve due to frequent operation.

[0038] To facilitate understanding of the specific implementation of this application, the following description will be provided in conjunction with the accompanying drawings.

[0039] See Figure 1 The figure is a flowchart of an ammonia injection quantity control method provided in an embodiment of this application, as shown below. Figure 1 As shown, this method is applied to a controller and includes:

[0040] S101: In response to engine start, sends a self-learning command to the engine.

[0041] In this embodiment, after detecting engine startup, the controller sends a self-learning command to the engine. This command instructs the engine to perform self-learning on the flow rate curve after the engine reaches a preset operating condition, in order to correct the flow rate curve. The flow rate curve represents the duty cycle of ammonia injection via the injection solenoid valve under different operating conditions, and this flow rate curve is stored in the controller's non-volatile memory (NVM).

[0042] S102: If it is determined that the ammonia in the SCR system is emptied and the engine operating conditions have reached the preset conditions, control the injection battery valve to inject ammonia according to the duty cycle under the preset conditions.

[0043] After the engine starts, it enters stoichiometric combustion. Upon receiving the self-learning command, the engine begins to purge the ammonia from the SCR system. Once the controller detects that the ammonia in the SCR system has been purged and the engine's operating conditions have reached the preset levels, it controls the injection solenoid valve to inject ammonia according to the preset duty cycle. It should be noted that during the self-learning process, the engine operates according to the preset conditions.

[0044] The controller can detect whether ammonia has been purged from the SCR system by acquiring the first tail gas concentration collected by the first sensor and the second tail gas concentration collected by the second sensor. If the absolute value of the difference between the first tail gas concentration and the second tail gas concentration is less than or equal to a third preset threshold, it is determined that ammonia has been purged from the SCR system. The first tail gas concentration is the nitrogen oxide concentration at the SCR inlet, and the second tail gas concentration is the nitrogen oxide concentration at the SCR outlet.

[0045] The third preset threshold is a number less than 1 and greater than or equal to 0, for example, the third preset threshold is 0.2. That is, when the difference in the concentration of the exhaust gas before and after passing through the SCR system is small, it is determined that the ammonia in the SCR system has been purged.

[0046] For example, setting it to NO at the entry point of the SCR system. x NO is installed at the sensor and the outlet. x Sensors, via front and rear NO x Sensors obtain NO before and after the SCR system x Concentration C NOx-Front C NOx-Rear If C NOx-Front -C NOx-Rear =0 indicates that the ammonia in the SCR system has been completely purged.

[0047] The process of the engine reaching a preset operating condition includes: acquiring engine operating parameters, which include one or more of speed, load, and exhaust flow rate; and determining that the engine operating condition has reached the preset operating condition if the value of the operating parameter is equal to a fourth preset threshold. The specific value of the fourth preset threshold can be set according to actual application conditions, and is not limited in this implementation.

[0048] It should be noted that the specific manifestation of the preset operating condition can be varied. For example, the preset operating condition is that the engine speed reaches the preset speed; or, the preset operating condition is that the engine load reaches the preset load; or, the preset operating condition is that the engine exhaust flow reaches the preset exhaust flow; or, the preset operating condition is that two of the above conditions reach the preset threshold at the same time; or the preset operating condition is that all three of the above conditions reach the preset threshold at the same time.

[0049] In this embodiment, after detecting that the engine's operating condition has reached a preset condition, the duty cycle corresponding to the preset condition can be determined based on the flow curve, so as to control the injection solenoid valve to inject ammonia gas according to the duty cycle.

[0050] S103: Obtain exhaust gas conversion efficiency.

[0051] After the injection solenoid valve injects ammonia gas according to the preset duty cycle, the NO in the SCR system can be reduced. x Perform a thorough restoration process. Simultaneously, it can be based on the before and after NO... x Sensors obtain exhaust gas conversion efficiency.

[0052] Specifically, through the pre- and post-NO x Sensors obtain NO before and after the SCR system x Concentration C NOx-Front C NOx-Rear Conversion efficiency η = (C NOx-Front -C NOx-Rear ) / C NOx-Front .

[0053] S104: If the exhaust gas conversion efficiency meets the preset conditions, the flow curve is corrected according to the exhaust gas conversion efficiency.

[0054] In this embodiment, the conditions for triggering correction can be preset. After obtaining the exhaust gas conversion efficiency, it is determined whether the exhaust gas conversion efficiency meets the preset conditions. If it does, it indicates that the NO in the exhaust gas discharged through the SCR system is within acceptable limits. x There is also untreated issue: the amount of ammonia injected by the solenoid valve is insufficient to reduce the NO in the exhaust gas. x To achieve a complete restoration, the flow rate of the solenoid valve needs to be corrected.

[0055] Specifically, the preset condition can be that the exhaust gas conversion efficiency is less than a first preset threshold, which is a value greater than 0 and less than or equal to 1. The specific value of the first preset threshold is determined based on the actual application; typically, it is a larger value between 0 and 1, for example, 0.8. Alternatively, the absolute value of the difference between the current exhaust gas conversion efficiency and the previous exhaust gas conversion efficiency is greater than a second preset threshold, which is a smaller value between 0 and 1, for example, 0.15. The previous exhaust gas conversion efficiency refers to the exhaust gas conversion efficiency corresponding to when the injection solenoid valve injected ammonia according to the duty cycle under the preset operating condition when the engine's operating condition reached the preset operating condition last time.

[0056] The correction of the flow curve based on the exhaust gas conversion efficiency can be implemented in the following ways:

[0057] One method is to use the reciprocal of the exhaust gas conversion rate as a correction factor, multiply the flow rate curve by the correction factor, and obtain the corrected flow rate curve. Since the exhaust gas conversion rate is at most equal to 1, when the exhaust gas conversion rate is 1, it indicates that the NO in the exhaust gas... x The gas has been fully recovered, and no correction to the flow curve is needed. Therefore, when correction to the flow curve is required, the exhaust gas conversion rate is less than 1, and thus the correction factor is greater than 1.

[0058] Another approach is to obtain the absolute value of the difference between the exhaust gas conversion efficiency and the previous moment's efficiency; determine a correction coefficient based on the absolute value of the difference and the corresponding relationship; and multiply the flow curve by the correction coefficient to obtain the corrected flow curve. That is, the correspondence between the absolute value of the difference in exhaust gas conversion efficiency between two adjacent moments and the correction coefficient can be pre-defined. During self-learning, this correspondence can be used to correct the flow curve so that the injection solenoid valve can fully reduce the NO in the exhaust gas when injecting ammonia according to the corrected flow curve. x This improves exhaust gas conversion efficiency and reduces pollution.

[0059] In some application scenarios, if the exhaust gas conversion efficiency does not meet the preset conditions, it indicates that the current exhaust gas conversion efficiency is high and there is no need to correct the flow curve. In this case, the engine operating conditions are obtained; the target duty cycle is determined based on the operating conditions and the flow curve; and the injection solenoid valve is controlled to inject ammonia gas according to the target duty cycle.

[0060] Among them, the exhaust gas conversion efficiency not meeting the preset conditions includes: the exhaust gas conversion efficiency is greater than or equal to the first preset threshold, or the absolute value of the difference between the exhaust gas conversion efficiency at the current moment and the exhaust gas conversion efficiency at the previous moment is less than or equal to the second preset threshold.

[0061] As can be seen, when the treated exhaust gas is found to contain nitrogen oxides, it indicates that the ammonia injection solenoid valve is aging, which causes a change in the actual ammonia injection volume. Therefore, the ammonia injection volume is self-learned so that the corrected flow curve can compensate for the problem of insufficient injection volume caused by the aging of the injection solenoid valve and improve the exhaust gas conversion efficiency.

[0062] For a better understanding of the specific implementation of this application, please refer to [link / reference]. Figure 2 The processing framework shown. Figure 2 The example shown uses the preset condition that the current exhaust gas conversion efficiency is not equal to the previous exhaust gas conversion efficiency as an example for illustration.

[0063] S201: After detecting engine start, the controller sends a self-learning command to the engine.

[0064] S202: The engine executes a self-learning command to clear the ammonia stored in the SCR system.

[0065] S203: The controller checks whether the ammonia in the SCR has been emptied. If yes, proceed to S204; otherwise, continue to S202.

[0066] S204: Obtain the current exhaust gas conversion efficiency.

[0067] S205: Determine whether the current exhaust gas conversion efficiency is equal to the previous exhaust gas conversion efficiency. If not, execute S206; if equal, end.

[0068] S206: The controller multiplies the flow curve by a correction factor to obtain the corrected flow curve.

[0069] The correction factor is determined based on the absolute value of the difference between the current exhaust gas conversion efficiency and the previous exhaust gas conversion efficiency, and the corresponding relationship, or the correction factor is equal to the reciprocal of the current exhaust gas conversion efficiency.

[0070] It should be noted that the specific implementation of each step in this embodiment can be found in [reference needed]. Figure 1 The relevant descriptions in the method embodiments shown are not repeated here.

[0071] Based on the above method embodiments, this application provides a controller, which will be described below with reference to the accompanying drawings.

[0072] See Figure 3 This figure is a controller structure diagram provided in an embodiment of this application, as shown below. Figure 3 As shown, the controller 300 includes: a sending unit 301, a control unit 302, an acquisition unit 303, and a correction unit 304.

[0073] The sending unit 301, in response to engine start, sends a self-learning command to the engine. The self-learning command is used to instruct the flow curve to be self-learned when the engine's operating condition reaches a preset operating condition. The flow curve is used to indicate the duty cycle of the injection solenoid valve when injecting ammonia under different operating conditions.

[0074] Control unit 302 is used to control the injection solenoid valve to inject ammonia according to the duty cycle under the preset operating conditions if it is determined that the ammonia in the selective catalytic reduction SCR unit is emptied and the engine operating conditions reach the preset operating conditions.

[0075] Acquisition unit 303 is used to acquire exhaust gas conversion efficiency;

[0076] The correction unit 304 is used to correct the flow curve according to the exhaust gas conversion efficiency if the exhaust gas conversion efficiency meets the preset conditions.

[0077] In some embodiments, the correction unit 304 is specifically used to correct the flow curve based on the exhaust gas conversion efficiency if the exhaust gas conversion efficiency is less than a first preset threshold; or, if the difference between the exhaust gas conversion efficiency and the exhaust gas conversion efficiency at the previous moment is greater than a second preset threshold, to correct the flow curve based on the exhaust gas conversion efficiency.

[0078] In some embodiments, the correction unit 304 is specifically used to use the reciprocal of the exhaust gas conversion rate as a correction coefficient, the correction coefficient being greater than 1; and to multiply the flow curve by the correction coefficient to obtain the corrected flow curve.

[0079] In some embodiments, the correction unit 304 is specifically used to obtain the absolute value of the difference between the exhaust gas conversion efficiency and the exhaust gas conversion efficiency at the previous moment; determine a correction coefficient based on the absolute value of the difference and the corresponding relationship, wherein the correction coefficient is greater than 1, and the corresponding relationship includes the absolute value of the difference and the correction coefficient corresponding to the absolute value of the difference; and multiply the flow curve by the correction coefficient to obtain the corrected flow curve.

[0080] In some embodiments, determining that ammonia has been purged from the selective catalytic reduction (SCR) unit includes: acquiring a first tail gas concentration collected by a first sensor and a second tail gas concentration collected by a second sensor, wherein the first tail gas concentration is the nitrogen oxide concentration at the inlet of the SCR unit and the second tail gas concentration is the nitrogen oxide concentration at the outlet of the SCR unit; if the difference between the first tail gas concentration and the second tail gas concentration is less than or equal to a second preset threshold, determining that ammonia has been purged from the SCR unit.

[0081] In some embodiments, determining that the engine's operating condition has reached a preset operating condition includes: acquiring the engine's operating parameters, which include one or more of speed, load, and exhaust flow rate; and determining that the engine's operating condition has reached the preset operating condition if the value of the operating parameter is equal to a fourth preset threshold.

[0082] In some embodiments, the apparatus further includes: a determining unit;

[0083] The acquisition unit 303 is also used to acquire the operating conditions of the engine if the exhaust gas conversion efficiency does not meet the preset conditions.

[0084] The determining unit is also used to determine the target duty cycle based on the operating conditions and the flow curve;

[0085] The control unit 302 is also used to control the injection solenoid valve to inject ammonia gas according to the target duty cycle.

[0086] It should be noted that the information execution process of each unit in the above-mentioned device can be found in the description of the method embodiment shown in the foregoing of this application, and will not be repeated here.

[0087] Additionally, see Figure 4 The figure shows a controller provided in an embodiment of this application. The controller 400 includes a memory 401 and a processor 402.

[0088] The memory 401 is used to store computer-readable instructions or computer programs;

[0089] The processor 402 is configured to read the computer-readable instructions or the computer program so that the device implements the ammonia injection flow control method.

[0090] This application embodiment also provides a vehicle, the vehicle 500 including: the aforementioned controller 501 and engine 502. The controller 500 can be either the aforementioned controller 300 or controller 400.

[0091] The controller 501 is used to control the injection solenoid valve in the engine 502 to inject ammonia gas according to a preset duty cycle;

[0092] The engine 502 is used to provide power to the vehicle.

[0093] This application provides a computer-readable storage medium, including instructions or a computer program, which, when run on a computer, causes the computer to execute the ammonia injection flow control method described above.

[0094] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0095] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0096] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0097] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0098] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An ammonia injection flow control method characterized by, The method is applied to a controller, and comprises: in response to engine starting, sending a self-learning instruction to the engine, the self-learning instruction being used to instruct self-learning of a flow curve when an operating condition of the engine reaches a preset condition, the flow curve being used to indicate a duty cycle of the injection solenoid valve when the engine injects ammonia gas under different operating conditions; if it is determined that ammonia gas in a selective catalytic reduction (SCR) device is emptied and the operating condition of the engine reaches the preset condition, controlling the injection solenoid valve to inject ammonia gas according to the duty cycle under the preset condition; obtaining an exhaust gas conversion efficiency; if the exhaust gas conversion efficiency meets a preset condition, correcting the flow curve according to the exhaust gas conversion efficiency.

2. The method of claim 1, wherein, if the exhaust gas conversion efficiency meets a preset condition, correcting the flow curve according to the exhaust gas conversion efficiency, comprising: if the exhaust gas conversion efficiency is less than a first preset threshold, correcting the flow curve according to the exhaust gas conversion efficiency; or if an absolute value of a difference between the exhaust gas conversion efficiency and an exhaust gas conversion efficiency at a previous moment is greater than a second preset threshold, correcting the flow curve according to the exhaust gas conversion efficiency.

3. The method according to claim 1 or 2, characterized in that, the correcting the flow curve according to the exhaust gas conversion efficiency, comprising: taking a reciprocal of the exhaust gas conversion efficiency as a correction coefficient, the correction coefficient being greater than 1; multiplying the flow curve by the correction coefficient to obtain a corrected flow curve.

4. The method according to claim 1 or 2, characterized in that, the correcting the flow curve according to the exhaust gas conversion efficiency, comprising: obtaining an absolute value of a difference between the exhaust gas conversion efficiency and an exhaust gas conversion efficiency at a previous moment; determining a correction coefficient based on the absolute value of the difference and a corresponding relationship, the correction coefficient being greater than 1, the corresponding relationship comprising correction coefficients corresponding to the absolute values of the differences; multiplying the flow curve by the correction coefficient to obtain a corrected flow curve.

5. The method of claim 1, wherein, the determining that ammonia gas in the selective catalytic reduction (SCR) device is emptied, comprising: obtaining a first exhaust gas concentration collected by a first sensor and a second exhaust gas concentration collected by a second sensor, the first exhaust gas concentration being a concentration of nitrogen oxides at an inlet of the SCR device, and the second exhaust gas concentration being a concentration of nitrogen oxides at an outlet of the SCR device; if an absolute value of a difference between the first exhaust gas concentration and the second exhaust gas concentration is less than or equal to a third preset threshold, determining that ammonia gas in the SCR device is emptied.

6. The method of claim 1, wherein, the determining that the operating condition of the engine reaches the preset condition, comprising: obtaining an operating parameter of the engine, the operating parameter comprising one or more of a speed, a load, and an exhaust flow rate; if a value of the operating parameter is equal to a fourth preset threshold, determining that the operating condition of the engine reaches the preset condition.

7. The method of claim 1, wherein, the method further comprising: if the exhaust gas conversion efficiency does not meet the preset condition, obtaining an operating condition of the engine; determining a target duty cycle based on the operating condition and the flow curve; controlling the injection solenoid valve to inject ammonia gas according to the target duty cycle.

8. A controller characterized by comprising: the controller, comprising: The sending unit sends a self-learning instruction to the engine in response to the engine starting, the self-learning instruction being used to instruct self-learning of a flow curve when a working condition of the engine reaches a preset working condition, the flow curve being used to indicate a duty cycle of the injection electromagnetic valve when the engine injects ammonia gas under different working conditions; The control unit controls the injection electromagnetic valve to inject ammonia gas according to the duty cycle under the preset working condition if it is determined that the ammonia gas in the selective catalytic reduction (SCR) device is emptied and the working condition of the engine reaches the preset working condition; The acquisition unit acquires an exhaust conversion efficiency; The correction unit corrects the flow curve according to the exhaust conversion efficiency if the exhaust conversion efficiency meets a preset condition.

9. A controller characterized by, The electronic device comprises: a memory and a processor; the memory is used to store computer readable instructions or computer programs; the processor is used to read the computer readable instructions or the computer programs, so that the electronic device executes any one of the methods in claims 1-7.

10. A vehicle characterized by comprising: The vehicle comprises: the controller in claim 8 or 9 and an engine; the controller is used to control an injection electromagnetic valve in the engine to inject ammonia gas according to a preset duty cycle; the engine is used to provide power for the vehicle.

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